suggested a symmetrical molecule, possibly consisting of two C6-C3 units
joined together as in lignoids. (Lignoids are discussed in Chapter VI;
they are natural products made of two or more phenylpropanoid units).
The mass spectral behavior of SC-1 was characteristic of that of the di-
arylbutanes (12). The mass peak (M+ 326) had a medium-low intensity of
25% as observed with similar methylenedioxy lignoids. Indeed, the methy-
lenedioxy benzyl or its equivalent was responsible for the base peak at
m/e 135. Other fragmentations were of very low abundance, with m/e 191
(MW-135, 2.3%) and m/e 163 (cleavage at the 8-8' bond, 3.1%) being the
most significant with respect to structural information, Figure 3.1. A
search of the literature showed possible identity of compound SC-1 with
austrobailignan-5 (13) with the structure 3.1. The agreement between SC-1
and austrobailignan-5 in the sign and magnitude of rotation indicated their
stereochemical identity.
Reaction of SC-1 with DDQ gave crystalline 3.2, C20H1604, with uv
absorbance at 239, 284, 315, 329 nm and pmr: T 2.29-3.50 (6 aromatic pro-
tons); T 4.04, 4.17 (2 methylenedioxy groups); T 7.62 and 7.94 (2 methyl
groups). These resembled the data given for the known 6,7-dimethoxy-4-
(3,4-dimethoxy)phenyl-2,3-dimethylnaphthalene (dehydrodimethyl guaiaretic
acid,3.3), (14) except for the differences of methoxyl versus methylene-
dioxy groups. Such 4-arylnaphthalenes are common dehydrogenation products
of various neolignans, although3.2 itself has not been previously described.

0 00 CH3ON0
yC CH.O S

3.2

3.3

m/e 326 (M ,

+

7+

m/e 135 (100%)

m/e 191 (1.1%)

m/e 1

Mass spectral fragmentations of SC-1.

Figure 3.1.

Compound SC-2
This is a colorless crystalline compound, C22H2805 (M+ 372), with uv
absorbance at 239 and 280 nm, and an optical rotation of [a]J20 + 48. The

pmr spectrum (see experimental) was relatively simple and characteristic
of a symmetrical molecule: six aromatic protons (T 3.17), two Ar-CH-0
(T 4.32 and 4.64), four methoxyl groups (r 6.14), and two CH-CH3 groups
(r 7.33, m; T 9.25, 9.33, d). The above information suggested a lignoid
structure,possibly of the tetrahydrofuran type. Since the ir did not
indicate the presence of hydroxyl or carbonyl groups, the fifth oxygen
might be considered as part of an ether function (1135 and 1160 cmn1).
Mass spectrometry was very useful for providing the overall structure of
SC-2. It has been amply demonstrated that the tetrahydrofuran function
can strongly direct fragmentation of lignoids possessing this nucleus.
This allows positional isomers of the tetrahydrofuran lignoids to be dif-
ferentiated via a well-defined fragmentation pattern (15). Spectral
analysis showed base at m/e 206, together with major peaks at 191, 175,
165, 151 and 138, all of which are characteristic of 2,5-bisaryltetrahy-
drofuran-type lignoids (Figure 3.2), and leading to 3.4 as the structure
for SC-2, with the stereochemistry to be decided.

H3 CH3

CH30- 0 0 OCH3

CH3 3.4 OCH3
Compound SC-3
SC-3 was obtained as a crystalline solid, C22Hzg2805 (M+ 372) with uv
absorption (Xmax 239 and 280 nm) and mass spectral fragmentations (base
peak m/e 206 and other peaks at 191, 175, 165, 151 and 138) identical to
compound SC-2. However, the pmr spectrum was rather more complex than that

7t

m/e 206 (100%)

m/e 165 (16%)

m/e 138 (11%)

m/e 191 (39%)

HCH3
HC-CH2
m/e 175 (37%)

m/e 151 (12%)

Figure 3.2. Major mass spectral fragments of SC-2.

of SC-2 (see experimental): a broad multiple T 2.89-3.13 due to six aro-

matic protons; two doublets T 4.87 and 5.56, corresponding to two benzylic

plet formed by two protons of the type CH-CH3; and, unlike SC-2, there

was a doublet for each methyl group, one at r 8.93 and the other at T 9.33.

The above data suggested a bisaryltetrahydrofuran structure for compound
SC-3 although the spectral differences could be ascribed to stereochemical

differences. Search of the literature and comparison of physical (mp 122-

1230, and [a]20 + 34) and spectral properties revealed SC-3 to be identi-

cal to the known lignoid veraguensin (16) with the structure 3.5.

CH30 0 0-- CH3

CH3 3.5 OCH3

Lignoids of the tetrahydrofuran type undergo an acid-catalyzed rear-
rangement to a 4-phenyltetralin system. Both 3.4 and 3.5 gave the same
product 3.6, C22H2604, when treated with p-toluenesulfonic acid; pmr:

2,4-dinitrophenyl hydrazine test, indicated that 3.7 had an aldehyde group,

presumably derived from the oxidation of one of the methyl groups. Cata-
lytic hydrogenation of 3.7 gave 3.3.

3.4 or 3.5 --3 3 )
CH30O CH3O-

0o 0o
3.6 OCH3 3.7 OCH3
CH3 CH3
With regard to the stereochemistry of SC-2, there are six possible
lignoids of this structure. Of these, two have the meso structure: gal-
gravin 3.8 (17) and tetrahydrofuroguaiacin 3.9 (18) and SC-2 differs from
both because of its optical activity. It differs also from two other
optically active isomers: galbelgin 3.10 (17) and veraguensin 3.5 (16).
Of the remaining hitherto unknown isomers 3.4 and 3.11, the pmr spectrum
of 3.11 must have signals due to nonequivalent aromatic protons and methyl
groups. Since SC-2 gave signals to indicate equivalent methyl (r 9.25,
9.33, d) and aromatic protons (T 3.17, s), and a generally symmetrical
structure, it must have the structure 3.4. SC-2 is thus a new compound.

A-^T-A0 A. A)^A
A 3 'Ar A 0r Ar Ar Ar
3.8 3. A 10 3.9

Ar 0 '"'Ar 3.1 Ar Ar 0 Ar
3.5 3.1_3.

Ar = 3,4-dimethoxy-benzene

Compound SC-10
The phenolic compound which was obtained as a crystalline solid (mp
204') did not show toxicity in mice. Elemental analysis and mass spectro-
metry indicated that the compound had a molecular weight of 328 correspond-
ing to C20H2404. It showed uv absorption maximum at 280 nm and upon addi-
tion of base, there was a shift of the maximum to higher wavelength, 295
nm. The ir spectrum (see experimental) indicated that it was aromatic and
it showed an intense hydroxyl band at 3440 cm 1. The pmr spectrum indicated
the presence of two active hydrogens (presumably phenolic groups) at T 2.35,
Figure 3.3. In the presence of D20, this signal disappeared, Figure 3.4.
The presence of the two phenolic hydroxyl groups was confirmed by the forma-
tion of a diacetate, C2H2806g, M+ 412; pmr: T 7.70, s, 3 H, T 7.80, s, 3 H.
Other groups indicated by the pmr spectrum were: five aromatic protons
(r 3.8-3-1), two aromatic o-methyl groups (Tr 6.2), three benzylic protons
(T 7.6, 2 H and r 6.67, 1 H) and two -CH-CH3 groups (r 8.45, m; T 9.17 and
8.95, two doublets). The mass spectral fragmentation of SC-10 showed im-
portant peaks at m/e 328 (Mi, base peak), 272, 241, 204, 189, 164 and 137,
which are characteristic of the 1-phenyl-l1,2,3,4-tetrahydronaphthalene lig-
noids (19). The molecular ion forms the base peak (m/e 328) as observed
in various phenyl-tetrahydronaphthalene lignoids such as isogalactin (19),
phyllanthin (20) and the podophyllotoxins (19). The m/e 164 can be attri-
buted to the structure 3.12, which is also consistent with the aromatic
substitution in the pmr spectrum. However, the most characteristic

0
HOX
OCH3
3.12

0 -- .-\ -.,
I-'

I,
--n
as

3 *)
.0
4-

0.

^~ ~~~ 1 -Ji
(-)

0~
2:- C,,?
:i 4

. g as ; (o

Ig : 2 = "
E4 a

4:L
11'~~ 6 .: j 5 .

Im
E g- l

"~~ ~~ f :{ii i

I

~i" I
ii
:Iii~

fragmentation is that,due to the reverse Diels-Alder reaction on the
parent compound (m/e 272) followed by loss of a methoxy group, m/e 241,
Figure 3.5.

Methylation of SC-10 and reaction with DDQ gave a crystalline solid,

C22H220s which was identical with 3.7 and gave the known 3.3 on catalytic
hydrogenation. These data and an optical rotation value of [a]20 + 42
indicated structure 3.13 for SC-10, identical with (+) guaiacin (21) in

structure and stereochemistry.

0 > > 3.7 > 3.3
H

3.13

T CH3
OH Experimental
General
Melting points were taken on a Fisher-Johns melting point apparatus.
All melting points are reported as uncorrected. Elemental analyses were
performed by Atlantic Microlab, Inc., Atlanta, GA. Ultraviolet spectra
were recorded on a Beckman Model 25 spectrophotometer. Infrared spectra
were recorded on a Beckman Acculab 3 infrared spectrophotometer. Samples
were examined as potassium bromide pellets (unless otherwise specified),

usually with a concentration of 1 mg of sample per 100 mg of potassium
bromide. All pellets were prepared with the aid of a minipress made by
Wilks Scientific Corporation.
Proton magnetic resonance spectra were recorded in deuteriochloroform
(CDC13) with tetramethylsilane (TMS) as the internal standard. Spectra
were obtained using a Varian T60A spectrometer: s = singlet, d = doublet,
t = triplet, q = quartet and m = multiple. Coupling constants (J) were
expressed in herz (Hz).

9.32, d, CH-CH.. The spectrum showed general characteristics of that of

a lignoid and specifically those of 2,5-bisaryltetrahydrofuranoid lig-

noids such as veraguensin and SC-2. The presence of a hydroxyl groups)

was confirmed by conversion to an acetate which showed ir band 1735 cm 1
42

0
z

I
U
00

(/)
1 '4-

SE

Iz u

E^ i

OJ a
ILI
0

zy

wzC )
0 cc
CLC
-3 r' S.-
"53-' -
S ~y~i : 0
SS'-' : C
Se ^ ff

0.

. j~ ~s G

'- S OS a)C
zs =g
wu^S z l a

and pmr signal T 7.80, s, characteristic of an acetate of an alcoholic
hydroxyl. The acetate also showed significant downfield shifts of the
doublet T 5.30, 5.40 to T 3.90, 4.00 and the multiple Tr 5.90 to T 5.47
thus suggesting that the hydroxyl is benzylic and was located in the vicin-
ity of the group 0-CH-CH3. The mass spectrum of SC-8 was not very useful;
it showed no molecular ion and no significant peaks above m/e 192. The
major peak was at m/e 165 which can be assigned to a dimethoxybenzoyl
fragment. Elemental analysis pointed to an empirical formula C21H2605-6
which, while showing relationship to a diaryltetrahydrofuranoid lignoid,
could not be relied upon for any further structural information.
In spite of the many points of similarity between SC-8 and a diaryl-
tetrahydrofuranoid lignoid 4.1, there are some discrepancies which cannot
be explained with such a structure. The most important one is the presence
of a benzylic hydroxyl. It cannot be located at either 2 or 5 positions
because: a) there will be no room for a "benzylic" proton and, b) the com-
pound would behave as a potential ketone similar to the lignoid magnolenin
C 4.2 described recently from these laboratories (24). The hydroxyl also
cannot be located at 3 or 4 or on the methyl groups because, according to
the pmr spectrum, there are two methyl groups, each attached to a -CH unit.
H3C CH3 CH3 CH30 O

veraguensin and SC-2 (see Chapter III) and still retained the hydroxyl
groupss. Also, the ratio between the aromatic protons and the methoxyl
protons in SC-8 could not be clearly defined and was in the range of 5:12
and 6:9.

Because of this, several other possibilities were considered for a
hypothetical structure to serve as a basis for further work. One of these,
4.4, is shown below. It has two different CH-CH3 groups, two benzylic pro-
tons, one next to a hydroxyl and another next to an ether and is, in gener-

al,in conformity with biogenetic considerations in the lignoid field. Such
a compound must generate on oxidation a methoxylated phthalic acid such as
m-hemipinic acid 4.5. Consequently, alkaline permanganate oxidation of
SC-8 was studied. Noneof the products recognized by their thin-layer
chromatographic or uv/pmr spectral behavior corresponded to either the
acid 4.5 or its isomer 4.6. Instead, the major products were found to be
veratric acid 4.7, 3,4-dimethoxyphenylglyoxalic acid 4.8 and an acid, the
methyl ester 4.9 of which had the molecular formula C20H2207 with the spec-
tral properties: uv, 285 and 307 nm; ir bands at 1700 and 1670 cm"1, char-
acteristic of a conjugated/aromatic ester and a ketone and pmr signals at:
T 2.33-3.17, m, 6 aromatic H; T 4.47, q, X-CH-CH3; T 6.14, s, 4 methoxyls
and T 8.19, 8.30, d, CH-CH3. The mass spectrum gave a molecular ion at m/e
374 and showed important peaks at m/e 343 (M-OCH3), 209 (M-165) and 165
(base peak, M-209). The base peak can be assigned to a dimethoxybenzoyl
fragment 4.10 and the peak at m/e 209 to the fragment 4.11, thus repre-
senting the fission of the molecule into two units.

CH3 OCH3
HO 4.9
CH3 0 4.12 0 > 49
CH30 0 COOCH3
Formation of 4.9 from SC-8 gave a basis for altering the hypothetical
structure 4.4 to 4.14 which contains many of the features known so far,
although the acid-catalyzed formation of cyclogalbelgin type of product
might be difficult to explain. In order to establish the nature of this
acid-transformation product, a more detailed study was undertaken of this
reaction. Treatment of SC-8 with p-toluenesulfonic acid in benzene gave
two products which were very difficult to separate from each other, in
contrast to veraguensin or SC-2 which smoothly gave cyclogalbelgin 4.3 as
the sole product. Separation of the two products was possible when it
was recognized that one of them was phenolic. The neutral fraction was
obtained as a colorless oil, C11H1403, with uv: 280 nm; ir: 1685 cm'1 and
pmr: T 3.25, m, 3 aromatic H; T 6.17, s, 2 OCH3; T 6.40, s, Ar-CH2 and
T 7.87, s, CH3-CO. These properties pointed to the structure of 3,4-
dimethoxyphenylacetone 4.15, which was confirmed by comparison with an

authentic sample prepared from 0-methylisoeugenol 4.16 by the action of
boron trifluoride.
OCH3

0 CH3 0 0 O
4.17, R:H CH3 4.20, R= CH3 OC
4.18, R COCH3 4.21, R=H R
4.19, R:CH3
Formation of aryl dihydronaphthalenes such as 4.17 is very character-
istic of the 2,5-diaryltetrahydrofuranoid neolignans and structures such
as 4.14 cannot satisfactorily explain this reaction. However, other struc-
tures might generate compounds such as 4.15 and formation of 4.17 alone
cannot be used as a proof for the possible existence of a 2,5-diaryltetra-
hydrofuran system in SC-8. To establish this point, SC-8 was subjected
to catalytic dehydrogenation with Pd/C reaction which is known to generate
a 2,5-diarylfuran. Two products were isolated from the reaction mixture:
a neutral compound and a phenolic compound. The former was a colorless
oil, C11H16,0, which was identical with an authentic sample of 3,4-dime-
thoxyphenylpropane 4.22 obtained from the catalytic hydrogenation of
0-methyl isoeugenol 4.16. The phenolic product 4.23 which showed pmr
spectral characteristics of a 2,5-diaryltetrahydrofuran on methylation
yielded a crystalline methyl ether 4.24, C22H,280,, pmr: T 3.17, 6 aromatic
H; T 5.32, 5.44, d, 2 Ar-CHO; T 6.17, s, 4 OCH3; T 8.17, m, 2 CH-CH3 and
T 8.90, 9.00, d, 2 CH-CH3. Compound 4.24 was found to be identical with
the known neolignan galbelgin.
4.23, R=H
SH4.24, R:CH3
CH30 OCH3 CH30O *i*
4.22 OCH3 OR
OCH3

Although the Pd/C reaction of SC-8 gave a diaryltetrahydrofuran deri-
vative instead of a diarylfuran derivative, the latter was obtained by
reaction of SC-8 with dichlorodicyanoquinone (DDQ). The product 4.25
showed uv-maxima at 283 and 325 nm and pmr spectrum in which the signals
due to the benzylic proton (AR-CH-0, T 4.50, 4.60) were absent and a
methyl signal (CH3 C =) appeared at T 7.70, thus indicating the presence
of a diarylfuran system. The remaining groups were intact: the aromatic
protons (T 2.80-3.17, m); Ar-CH-OH (r 5.27-5.44, d); methoxyl (T 6.04,
6.14, s) and CH-CHj (T 8.77, 8.87, d). Compound 4.25 was then subjected
to catalytic dehydrogenation (Pd/C) followed by methylation to yield a
crystalline solid 4.26 with uv maxima 252 and 326 nm and pmr: T 2.74-3.05,
m, 6 H; T 6.19, s, 12 H; T 7.80, s, 6 H, identical with the known 2,5-bis-
(3,4-dimethoxy)phenyl-3,4-dimethylfuran (14).

4.25, RC,,H,,1503

XO O OCH3 4.26, R-CH3
OR

From the foregoing data, it is clear that SC-8 does have a 2,5-diaryl-
tetrahydrofuran system, as indicated by the isolation of 4.24 and 4.26
and even 4.19 through acid-catalyzed transformation, which is characteris-
tic of such a system. However, the formation of the acid 4.9 as well as the
pmr spectrum with signals for Ar-CH-OH and 0-CH-CH3 clearly indicate the
presence of other functionalities not normally seen in a diaryltetrahydro-
furan system. Also, each of the reactions described above, dehydrogenation
with Pd/C and acid-catalyzed transformation, gave a neutral product and a
phenolic product, either a diaryltetrahydrofuran or an aryltetralin, thus
suggesting that the neutral fragments were attached to the phenolic hydroxyl

of each of the aryl groups and were cleaved in the process. All these
observations can be reconciled by a structure such as 4.27i.in which a cen-

tral diaryltetrahydrofuran system with a phenolic group on each of its
aryl groups is attached to a phenylpropanoid unit (C9). A proof for such
a structure was obtained by a careful analysis of the products of the acid-
catalyzed transformation. It was found that the ratio between the ketone
4.15 and the phenol 4.17 was 2:1, thus showing that two C9 units (ketone)
were joined to the aryl tetralin system and hence, a diaryltetrahydrofuran
system. OCH

and three were methyl carbons. This information, coupled with the chemical
shifts and the pmr data indicating three methoxyls and possibly six aro-
matic protons, allowed the following assignment for the 13C nmr spectrum of
SC-8: 6 150.4, 148.9, 148.7, 146.3, 136.2 and 132.6 (6 40 aromatic car-
bons); 6 83.6 and 83.2 (2 Ar-CH-0); 6 78.1 (CH3-CH-O), 6 55.7 (3-OCH3);
6 44.0 (CH-CH3); 6 16.8 and 14.7 (2 CH-CH ).
The 13C nmr spectrum agreed very well with information obtained from
the pmr spectrum and suggested the probability of at least one element of
symmetry in the compound, since there are fewer observable carbon-types

that of SC-8, the only differences being due to the integration values.

For example, the CHCH, doublets as well as Ar-CH-0/Ar-CH-OH showed a ratio

of 2:1 instead of the 1:1 observed with compound SC-8. Similarly, the
ratio of aromatic H/methoxyl H was 1:1.33 instead of 1:1.5. The presence

of hydroxyl groups was confirmed by acetylation to a diacetate C35H401,o,

1735, 1760 cm'1 and T 7.70, s, 3 H, T 8.00, s, 3 H, in which one alcoholic
(benzylic) and one phenolic hydroxyl were involved. SC-6 underwent acid-
catalyzed rearrangement with formation of the same components seen with
SC-8, 4.15 and 4.17 but in a 1:1 molar ratio. Thus, SC-6 is assigned

structure 4.30, identical to SC-8 except for the absence of one of the
3,4-dimethoxyphenylpropanoid units. Furthermore, confirmation of the
structures 4.30 for SC-6 and 4.27a for SC-8 was obtained via conversion

of SC-6 to SC-8. This was accomplished by the alkylation of SC-6 with
3,4-dimethoxy-2'-bromopropiophenone to yield 4.31. The ketone 4.31 was
then reduced with sodium borohydride whereby a mixture of the two dia-
stereomers 4.27e,b was obtained.

56

o
C,

o

in
i E

ac

I.3

o
W U) 4J
0 0

C-)

,L M ) E

~ za
^- -

SZz.S =
^ ^ ^ss
S5 32S
Ij^ sij .

4.30 HO- ) U CH

CHH3 OCH
C H 30 3]O OCH3

4.30 --0> 9` 431 X ---- > 4.27a,b

Stereochemistry of SC-6, 7 and 8
Compounds SC-6, 7 and 8 contain six to eight asymmetric carbons,
corresponding to as many as sixty-four to two hundred and fifty-six pos-
sible stereoisomers. To simplify the task of elucidating the stereochem-
istry of these compounds it was found convenient to divide the molecule in-
to two units: a) the 2,5-diaryltetrahydrofuran system and, b) the phenyl-
propanoid-0-aryl system.
The tetrahydrofuran system was discussed in detail under the stereo-
chemical elucidation of SC-2, at which time it was observed that the pmr
seemed to be a very useful tool for the analysis of the six possible repre-
sentations of the 2,5-diaryltetrahydrofuran system: galbelgin 4.24 (17),
galgravin 4.32 (17), veraguensin 4.33 (16), tetrahydrofuroguaiacin 4.34
(18), SC-2 4.35, and an unknown lignoid 4.36. In the pmr analysis of these
compounds, the benzylic protons (Ar-CH-0) are clearly sensitive to the
orientation of the aryl groups, and their chemical shifts can be used to
differentiate the various isomers. Furthermore, structures with equivalent

This type of analysis allows us now to study the stereochemistry of
the SC-lignoids with respect to the tetrahydrofuran system. The pmr spec-

tra of SC-6, 7 and 8 were found to resemble that of SC-2 closely (Table 4.1)

and were very different from that of the other possible isomers, thus giving

a clear indication of a 2:3-cis/3:4-trans/4:5 cis arrangement for the four

substituents on the tetrahydrofuran ring, identical to that seen in SC-2.

Further evidence for this type of system was obtained from the 13C-nnr spectrum.

Here, a pattern can be seen, in which the signal due to the benzylic carbon

C-2 (or C-5) is located at 6 82-83 ppm if the aryl substituent is cis to

the methyl group at C-3 (or C-4), and at 6 87-88 ppm if the groups are trans

(23). Comparison of the 6 values of the methines at C-2 and C-5 (Table 4.2)

with the reported values of the known isomers, indicated that SC-8 corre-
sponded to a 2-3 cis/4-5 cis system. In support of this, we observed ear-
lier the ready isomerization of SC-8 to the more stable, all-trans, galbel-
gin 4.24 system when heated with Pd/C.

Table 4.1. Comparison of pmr data (c) of SC-6, 7 and 8 with that of
related lignoids

Lignoids CH3-CH Ar-CH-0

8.95 (d), 3 H 5.52 (d), 1 H
9.35 (d), 3 H 4.90 (d), 1 H

Galbelgin 4.24 8.95 (d), 6 H 5.40 (m), 2 H

Galgravin 4.32 8.95 (d), 6 H 5.47 (m), 2 H

SC-2 4.35 9.30 (d), 6 H 4.48 (d), 2 H

SC-8 9.27 (d), 6 H 4.55 (d), 2 H

SC-7 9.28 (d), 6 H 4.57 (d), 2 H

C-6 9.30 (d), 6 H 4.57 (d), 2 H

Table 4.2. Comparison of the '3C-nmr of SC-8with that of related lignoids

Finally, we should consider the stereochemistry of SC-6, 7 and 8 at
the phenylpropanoid-0-aryl system. Compounds which incorporate this sys-
tem were originally obtained from the oxidative coupling of isoeugenol
(25) (4.37, 4.38) and since then, two natural products of similar structure,
virolin 4.39 and surinamensin 4.40, have been isolated (26). Of the two
possible isomers, the erythro isomer 4.37 was obtained from the corre-
sponding ketone 4.41 by reduction with sodium borohydride while the threo

RI HO HO
0 OH 0 H O
OCH3 CH3 H

H OCH3 CH3O H CH3

4.38 4.41
4.37, R1- R- H

4.39, R CHH R2 H

4.40, RI-CH3 R2= OCH3

form was formed exclusively through the enzyme-H202 catalyzed coupling
reaction (25) which formed the dimer. The two isomers can be differentiated
by comparing their respective chemical shift of the 7-methine and the cou-
pling constant (erythro: T 5.15, J = 3; threo: T 5.38, J = 8). The pmr
spectra of SC-6, 7 and 8 showed doublets at T 5.35 with J value of 8,
clearly indicating the threo configuration as reported for virolin and
surinamensin (26). The unperturbed doublet structure also indicates that
both phenylpropanoid chains have the same threo configuration. In con-
trast, the semisynthetic SC-8 4.27b shows signals due to both isomers:

with a saturated solution of p-toluenesulfonic acid (5 ml) for two hours.
When the tic (15% acetone-benzene) showed the absence of SC-8 and forma-
tion of two higher Rf band, the cooled mixture was partitioned with hexane-

benzene-methanol-0.5 N NaOH (1:1:1:1) to separate the neutral from acidic